So the back is also covered with components, so the heatsync will be on both the front and back - a bit like the JDB's do it, with an aluminum plate that screws down to make contact. Really it's the right side (where the battery terminals are) that needs the heat dissipation more than the left side, and we have done the thermal modeling to see how it should heat, but ultimately when it's under real load it's nice to see it happen in the real world. As I said, even at 100-150a it should be fine without heat syncs, but you wouldn't want to push it beyond that.
In terms of how it would be oriented for cases, it's designed to go into our systems, so I don't have any experience with other cases that are out there - we did match up a couple of the screw holes to a similar JK BMS, so you might be able to use the same mounting points, although the cable attachments might need to be different. We really didn't design it to be a drop in replacement for a JK or JBD, etc - so that's probably not going to be the best use case for it, you're probably better off just sticking with whatever the case is designed for. At some point we may design a rack mount case specifically for this, but that's a ways off as we do more software and hardware design work and not mechanical engineering.
FWIW, I've designed a 3D printed Eve 280-300ah prismatic cell holder, like those ABS one you can buy from China, and I'll be posting up the STL and pictures in a couple weeks for anyone who's interested in making anything like that. I print them with PETG, and assuming you're getting a decent price on your filament, it comes out to about the same cost as the Chinese ones, but when you factor in not paying for shipping it's much cheaper - plus it's fun to print them and mine have some different design elements I think are cool. We use 80/20 quite a bit, so they're designed to 'lock' into the channels on the 15 series (both from the bottom and top), and the sides of the brackets lock into eachother as well - and I just use fiber reinforced tape around it to keep it kind of locked together until it's mounted into the 80/20. On the top the channels also ensure that the 80/20 can't come in contact with the terminals, which would clearly be bad.